More on environment, exercise and hip dysplasia
I came across another study detailing how important the control of exercise and environment is in a young puppy/dog to help prevent hip dysplasia. Breeders do their job by implementing good screening, breeding, and puppy rearing practices, but the work doesn't end when a pup goes home.
According to this 2012 study:
Puppies walking on stairs from birth to 3 months of age had an increased risk of developing HD. Factors associated with a decreased risk of developing HD included off-leash exercise from birth to 3 months of age, birth during the spring and summer, and birth on a farm.